Medical device comprising an artificial contractile structure

ABSTRACT

A medical device includes an artificial contractile structure which may be advantageously used to assist the functioning of a hollow organ, an artificial contractile structure including at least one contractile element ( 100 ) adapted to contract an organ, in such way that the contractile element ( 100 ) is in a resting or in an activated position, at least one actuator designed to activate the contractile structure, and at least one source of energy for powering the actuator. The ratio “current which is needed to maintain the contractile element in its activated position and in its resting position/current which is needed to change the position of the contractile element” is less than 1/500, preferably less than 1/800, and more preferably less than 1/1000. The medical device further includes elements for reducing corrosion of the medical device.

TECHNICAL FIELD

The present invention relates to a medical device comprising anartificial contractile structure activated by an actuator, which may beadvantageously used to assist the functioning of an organ, e.g. asphincter or the heart. More generally, it can be used for moving orconstricting a hollow or a tubular part of the body in such a way as toreduce its diameter.

BACKGROUND OF THE INVENTION

It is known to use artificial structures to assist muscular contraction.Such structures are adapted to assist atrial or ventricular contraction,or to assist or replace a natural sphincter. The use of such artificialsphincters has increased in recent years because faecal and urinaryincontinences now affects more than 10% of people over 60 years of ageand dramatically increases in patients over 80 years of age. Severalpharmaceutical or surgical solutions have been developed for treatingurinary and faecal incontinences. Generally, the outcome of surgery fortreatment of urinary and faecal incontinence has to be regarded as low.The impacts on health care costs and overall quality of life of thepatient are enormous.

The AMS800 artificial sphincter for urinary incontinence iscommercialized by American Medical Systems and is composed of threecomponents, a cuff, a pump, and a pressure-regulating balloon. The cuffis implanted at the bulbous urethra in males and is inflatable by meansof a fluid. The pump is implanted in the scrotum and thepressure-regulating balloon is implanted in the abdomen. The majorproblems when using AMS800 is the tissue erosion around the urethra dueto the constant pressure, the atrophy and irritation of tissues at thelocation of the inflatable cuff, and the emergency surgery for repairshould the device remain in closed position in the event of mechanicalfailure. All other commercialized artificial sphincters whether forurinary or faecal incontinences bear similar drawbacks.

The ProAct™ device for urinary incontinence is commercialized byUromedica and is composed of two small implantable balloons. During ashort outpatient procedure, the balloons are surgically placed under theskin in the area where the prostate of the patient was surgicallytreated. The balloons help protect against accidental leaking of urineby increasing the amount of pressure required to urinate. When thepatient needs to urinate, a normal amount of effort still should berequired to push the urine out. However, the pressure from the balloonswill help guard against unintentional urine loss, such as during asneeze or cough. The major problems when using ProACT™ are identical tothe problems using AMS800 artificial sphincter described above.

FlowSecure™, manufactured by Sterilin Ltd, another silicone hydraulicurinary sphincter similar to AMS800, has an extra pressure transmissionballoon to transfer increased intra abdominal pressure directly to thecuff. Implantation of this device is technically feasible, but stilldifficult and is reported to be safe and effective in the short-term forthe treatment of male urodynamic stress urinary incontinence, arisingfrom a number of etiologies. However, the major problems when usingFlowSecure™ are identical to the problems using AMS800 artificialsphincter described above.

Some publications describe the use of artificial sphincters comprisingshape memory alloy elements suitable for opening and closing a part ofan organ in a living body.

JP 07-051304 discloses a constrictor comprising two shape memory alloyelements with different shape memories, and covered by coveringmaterials.

The first covering material is formed in a shape to close the urethra inthe daytime, and the second covering material is formed in a shape tohalf close the urethra in the night. This sphincter allows changing thepressure to the urethra, in order to prevent the incontinence in lifeaction in the daytime, and to avoid necrosis of the tissue by loosingthe pressure to the urethra in the night.

However, the drawbacks of such artificial sphincters are that there is arisk of tissue erosion and consequential necrosis, due to the highconstant pressure to the urethra during the day and that there is a riskof incontinence during the night. If the shape memory alloy is no moreefficient or is broken, the whole sphincter should be moved andreplaced. Another risk is tissue erosion due to the high temperature ofthe shape memory alloy.

Moreover, JP 07-051304 discloses an artificial sphincter in which theshape memory alloy elements are disconnected from each other. Thisembodiment does not allow optimal pressure control.

Moreover, this kind of shape memory alloy elements uses a lot of power.That means that the battery needs to be changed very often oralternatively very large batteries have to be used.

EP 1 598 030 discloses an urine incontinence treatment apparatus,comprising a restriction device for engaging the urethra to form arestricted urine passageway in the urethra, the restriction device beingoperable to change the restriction of the urine passageway, a source ofenergy, and a control device operable from outside the patient's bodyfor controlling the source of energy to release energy for use inconnection with the operation of the restriction device, a motor or pumpimplantable in the patient, wherein the source of energy is adapted topower the motor or pump and the control device is adapted to control themotor or pump to operate the restriction device. The source of energycan be an internal battery with a lifetime of at least 10 years.However, as disclosed in EP 1 598 030, an internal battery is anadvantageous solution for embodiments of the apparatus that have arelatively high consumption of energy, which cannot be satisfied bydirect supply of wireless energy. Therefore, even if the lifetime of theinternal battery is of 10 years, the operation time of said internalbattery is shorter as the energy consumption is very high. Said internalbattery should therefore be changed very often.

WO 2009/048399 discloses an apparatus for controlling a flow of spermsin an uterine tube, comprising an implantable flow influence device tobe applied on at least one portion of the uterine tube. The energysource is an implantable primary battery or accumulator. Preferably theenergy source is external and a control device controls the externalenergy source to transmit wireless energy from the outside of thepatient's body to the inside. The energy will directly be used or theoperation of the device e.g. to power the constriction/stimulation unit.The internal source may store energy. The constriction/stimulationdevice needs high energy to be activated but also to be maintained in anactivated position. Therefore the preferable energy supply is thewireless transmission of energy. A drawback of wireless transmission isits efficiency. In case of using an accumulator for storing energy theaccumulator has to be recharged frequently that reduces the lifetime ofthe accumulator.

WO 2009/004092 discloses an artificial structure comprising severalcontractile elements adapted to contract an organ by means ofcontractile fibers. Such fibers need high energy to be activated butalso to be maintained in an activated position. As disclosed in WO2009/004092 an implanted rechargeable battery needs to be recharged atleast once a day using a battery volume in the range of this invention.Larger rechargeable batteries with more capacity exist but would not bepossible to implant.

WO 2004/066879 discloses a male sexual impotence treatment apparatus,comprising a constriction member extending in a loop around the peniletissue. Wireless energy transfer is used to electrically power theconstriction member during device operation that means external energyis wireless transmitted from the outside of the patient's body to theinside to recharge the implantable battery. The energy will directly beused or the operation of the device or to recharge the battery. Theactuator is fixed on the constriction member in such a way that anelectric wire linking the actuator to a source of energy goes throughthe body of the patient. A drawback of wireless transmission is itsefficiency. Another drawback is the recharging of the battery. Smallrechargeable batteries have to be replaced after about 1 year.

Moreover, the electric wire should be designed to conduct a current inthe order of milliamperes, which is needed for powering the operationdevice when operating the constriction device, so that the constrictiondevice exerts a force strong enough to constrict the penile tissue orthe prolongation thereof, so that the patient's penile exit blood flowis restricted. Thus the electric wire should have a low resistance.

No information is given, how much energy is needed to constrict thepenile tissue and for how long. Based on the description and thedrawings, continuous power is needed to hold the device in constrictposition.

WO 2007/066344 discloses an implantable extra cardiac compression devicefor left ventricular assistance in severe heart failure. The devicecomprises metal flanges that are passively flexed at springed-hinges bya vertically moving metal cup. The flanges are connected to each otherby a high-tensile, elastic polymer membrane. However, with such device,one flange, used alone, cannot contract the organ. Moreover, such deviceneeds high energy to be activated but also to be maintained in anactivated position. The external battery that may be recharged will beconnected transcutaneously to the motor assembly placed inside thepatient's abdomen. A transcutaneous connection always bears a risk ofinfection.

Moreover, when such implantable devices are placed in the body of apatient, they are on contact with body fluids. Moisture penetrates intothe device and more specifically into the control unit and the actuator.Moisture condenses, and water propagates and reaches the control unit,in which corrosion starts. The drawback is that some parts are corroded,and more specifically, the electronic and mechanical parts of thecontrol unit and the actuator.

U.S. Pat. No. 7,011,621 discloses a body fluid flow control devicecomprises a first engaging element and a second engaging element (calledplunging member) forming an inner diameter when second member movestowards first member to encircle a body vessel. That means the plungingmember moves and press one side of the organ. With other words motordrives the worm gear pulling the nut along with the casing and thus actson the cable to push the plunging member to close the body fluid flowcontrol or to pull on the plunging member using the cable to open thebody fluid flow control. The described design has several disadvantages.First pushing the plunging member needs a quite stiff cable to apply thenecessary pressure towards the vessel. Otherwise the cable would kink.Patient feels stiff sleeve including cable. The bending radius of astiff cable is limited. This will limit the indications, e.g. theimplantation of such a device close to the bladder neck is almostimpossible. Second the inner diameter that is formed when the plungingmember is moved towards the first engaging member is just in one limitedcase a circle, namely when the radius of the first engaging member andthe plunging member are the same. Otherwise, and this will be the normalcase using this design the enclosing form is like a lens or an ovalleading to not evenly distributed pressure on the vessel. That meansthere are areas where the tissue will be compressed more than in otherareas leading to tissue damage. Further the circumference of the vesselcould be much bigger that the circumference built by the two members.That means that by moving the plunging member towards the first membervessel will be squeezed without being closed resulting in tissue damage.On the other hand the circumference of the vessel could be smaller thanthe circumference of the two members meaning that the vessel stays open,even the members are closed. Further, the vessel is pressed all the timeexcept when e.g. the patient has to void. This leads to the same problemas for AMS 800 namely to tissue erosion around the vessel due to theconstant pressure, the atrophy and irritation of tissues.

The disclosed concept is very energy consuming because energy is neededto maintain the closed position. There is no mechanism described thatwould keep the device in its closed position. Moreover in case of nopower the closed position of the members cannot be hold because ofvessel pressure and the motors turn back to a balanced position. But inthis position the vessel is not closed anymore.

Moreover, U.S. Pat. No. 7,011,621 discloses the use of a magneticcoupling device placed between the casing and the cable. In thisconfiguration, the magnetic field is not well shielded. That means thatthe magnetic field of the magnets will influence the reliability of theelectromotor.

WO 99/48438 discloses an artificial sphincter system which comprises afirst shell and a second shell for coupling with the second shell toform a cylindrical objective suitable for engaging and surrounding aselected canal with the host body. It also includes a plunger forconstricting the fluid flow when activated. The host-user can activatethe sphincter system with a remote control. The device also comprises acasing containing a piston-like mechanism for driving a plunger into thehollow portion of the device to restrict fluid flow through the canalenveloped by the device. The piston-like mechanism is preferably anelectromechanical solenoid but any hydraulic, pneumatic, or equivalentpiston-like mechanism can be used.

Piston-like or plunging member need power be stay in closed position. Noinformation is provided about how much energy (current) is needed toopen and close the piston-like or plunging member and keep closedposition meaning continuous current would be needed to keep thesphincter closed.

US 2005/148814 discloses an electromechanical apparatus and methoduseful for augmenting muscle function. The method involves operatingelectrically operated actuators on an external surface of the muscle ororgan. The carrier comprises electrically operated actuators arranged ina band, mesh, or other suitable arrangement. In some embodiments of theinvention, the carrier has a band-like, tubular or cuff-like shape thatfacilitates the carrier at least partially encircling the organ.

The control system includes a (Analog-to-digital) ADC conversion systemwhich provides processor system with digital signals corresponding tothe analog bioelectronic signals picked up from the organ by electrode.The control system includes also a (Digital-to-analog) DAC system whichprovides carrier with analog signals that causes it to compress andrelax in response to the digital output signals computed processorsystem.

This means that the apparatus needs to be regularly powered.

Moreover, in operation, in essentially the manner of a conventionalsolenoid, currents in wire coils create magnetic fields andcorresponding forces upon magnetized members. The resulting movement ofthe members contract the mesh of actuators causing carrier to compressthe organ to which it is applied. When the current is removed, the meshexpands again.

That means that a continuous current is needed for compressing theorgan.

Therefore there are, at the present time, no adequate solutions, whethercommercial or in the literature, for implanting robust devicescomprising an artificial contractile structure.

SUMMARY OF THE INVENTION

The present invention provides an implanted medical device comprising anartificial contractile structure which allows to avoid the disadvantagesof the prior art.

Accordingly, the present invention relates to a medical devicecomprising:

-   -   an implantable artificial contractile structure comprising at        least one contractile element adapted to contract an organ, in        such way that said contractile element is in a resting or in an        activated position, the activated position being defined with        said contractile element constricting the organ and the resting        position being defined with said contractile element not        constricting the organ,    -   at least one actuator,    -   at least one control unit comprising and controlling said        actuator, and    -   at least one source of energy for powering said actuator.

According to the invention, said actuator is designed to activate saidcontractile structure in such a way that the ratio “current which isneeded to maintain the contractile element in its activated position andits resting position/current which is needed to change the position ofthe contractile element and to move it between its activated positionand its resting position” is less than 1/500, preferably less than1/800, and more preferably less than 1/1000. Said medical device furthercomprises means for reducing corrosion, and more especially means forreducing corrosion in the control unit.

One of these means for reducing corrosion in the control unit consist inthat at least a part of the transmission means, which are designed totransmit to the contractile element a force induced by the actuator, isintegrated in said contractile element.

One of these means for reducing corrosion in the control unit consist inthat the control unit comprises at least one first chamber, which ishermetically sealed and may contain the elements which are the mostsensitive to moisture, and on its side facing the contractile element,at least one second chamber, which is not hermetically sealed and whichcontains a part of the transmission means. At least one magneticcoupling device is used for communicating energy provided in the firstchamber to the second chamber.

In case the medical device comprises a source of energy placed in apower supply unit separated from the control unit and connected to saidcontrol unit with electric cables, one of these means for reducingcorrosion in the medical device consist in providing a currentconversion DC/AC/DC between the power supply unit and the control unit.

Advantageously, the present invention provides a medical devicecomprising an artificial contractile structure which is designed forchronic applications (i.e. long-term implantation), for example for manymonths and preferably many years.

Such devices may be used in several indications, e.g. for assisting orreplacing a natural sphincter, especially for the treatment of faecal orurinary incontinence, for assisting atrial or ventricular contraction,for assisting the respiratory function, for assisting or replacing aparalyzed muscle or for treating venous insufficiency. The presentinvention is particularly designed for improving sphincter musclefunction and therefore to improve the patient's quality of life with asignificant reduction of treatment costs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a medical device according to the presentinvention,

FIG. 2 represents a schematic view of a first embodiment of thecontractile element used in the invention,

FIG. 3 represents a schematic view of a second embodiment of thecontractile element used in the invention,

FIG. 4 is a schematic view of an actuator used in the invention,

FIG. 5 represents the cycle time as a function of the operating time fora device of the invention using primary batteries,

FIG. 6 is a detailed side view of a preferred embodiment of the magneticcoupling device, and

FIG. 7 is a detailed perspective view of a preferred embodiment of themagnetic coupling device.

DETAILED DESCRIPTION

In the present description, the term “organ” covers any organ of thehuman body, preferably an organ comprising a hollow part, containingfluids as for example the ventricular part of the heart, or a region ofan organ in the living body having an overall cylindrical shape, forexample a blood vessel, the urinary tract, the colon, the stomach or anyother body part against which pressure can be applied.

In the present description, the term “electromotor” covers any devicedesigned to produce motion and mechanical effects by the action ofelectricity.

In the present description, the term “constrict” means that thecontractile element applies a pressure against a region of an organaround or on which said contractile element has been placed.

In the present description, the term “pulsatory” means that eachcontractile element is activated and deactivated in alternation withanother contractile element to constrict or apply a pressure or notagainst the region of the organ or the hollow part around or on which ithas been placed, preferably so as to close or open said region of theorgan or of the hollow part. More especially, in a preferred embodiment,contractile element one is closed for a certain time, while the othercontractile element(s) are open. After a given time the contractileelement two will be closed while the contractile element one is stillclosed. When contractile element two is closed, contractile element oneopens, and so on. The frequency of alternate activation is dependentupon the nature of the tissues and inside organ pressure, and isadjusted so that no tissue erosion and burn appear after several monthsof implantation.

In the present description, the term “continuous” means that a pressureis applied against at least one region of the organ in such a way thatsaid organ is closed during all the time for which the medical device isused, except the short periods for which the organ should be open.

In the present description, the term “link” means a direct or indirectconnection between two elements.

The medical device comprises:

-   -   an artificial contractile structure comprising at least one        contractile element adapted to contract an organ, in such way        that said contractile element is in a resting or in an activated        position, the activated position being defined with said        contractile element constricting the organ and the resting        position being defined with said contractile element not        constricting the organ,    -   at least one actuator designed to activate said contractile        structure and separated from the contractile structure,    -   at least one control unit comprising and controlling the        actuator,    -   at least one source of energy for powering said actuator.

Preferably, said actuator comprises at least one electromotor providedwith a gearhead and transmission means linked to the contractile elementand designed to transmit to the contractile element a force induced bythe electromotor.

Advantageously, the actuator is separated from the contractilestructure. That means that the actuator is linked to but not fastened onthe contractile structure or on the contractile element.

According to the present invention, said medical device furthercomprises means for reducing corrosion, and more particularly in thecontrol unit.

One of these means for reducing corrosion in the control unit consist inthat the control unit comprises at least one first chamber, which ishermetically sealed and contains elements which are the most sensitiveto moisture, as for example the electromotor and its gearhead, and onits side facing the contractile element, at least one second chamber,which is not hermetically sealed and which contains a part of thetransmission means.

The first chamber may also contain other electronics, as printed circuitboards and position sensors.

The second chamber is designed in such a way that the transmission meansexit from said second chamber in direction of the contractile element.

Advantageously, the first chamber is sealed to the walls of the secondchamber by means of a laser seam weld. The first and second chamber maybe made of titanium.

The first and second chambers may be placed in the same housing, madefor example of titanium.

According to another embodiment, this housing may further comprise athird chamber, which is also hermetically sealed and may containelements which are sensitive to moisture and which are not placed in thefirst chamber.

In this embodiment, the electromotor and its gearhead may be placed inthe first chamber, and electronics as printed circuit boards andposition sensors may be placed in the third chamber.

The elements which are placed in the first and/or third hermeticallysealed chambers are not necessary made of biocompatible material.

Having the motor and its gearhead placed in the first chamber and theelectronics placed in the third chamber has the advantage to use a brushmotor. Indeed in that case, dust coming from the brushes will remain inthe first chamber and cannot interfere with the electronics placed inthe third chamber. Brush motors have the advantage that they have thesimpler electronic which make them more reliable.

Advantageously, the actuator further comprises a magnetic couplingdevice designed to transmit to the contractile element a force inducedby the electromotor. Preferably, said magnetic coupling device is placedat the end of the gearhead of the electromotor.

Preferably, said magnetic coupling device comprises a first magnetplaced in the first chamber and a second magnet placed in the secondchamber. The thin titanium wall of the second chamber, which separatesthe first magnet from the second magnet, constitutes a flat hermeticseal. The magnets may be placed advantageously on each side of said flathermetic seal, one behind the other. The use of flat surfaces allowshaving simple design which is easy to produce, contrary to the designdisclosed in U.S. Pat. No. 7,011,621. The magnets may be encapsulated,for example in titanium.

Moreover, advantageously, the magnetic field of the magnets that are oneach side of the flat seal can be reduced with metal plates to avoid anydysfunction of the electromotor. Shielding the magnetic fields requestsa proper position of the Hall sensor which may be used as positionsensor, close to the second magnet because of the reduced magneticfield. More than one Hall sensor could be placed.

In a preferred embodiment, the actuator may comprise an electric motor,a gearhead connected to said motor, a lead screw and a nut mounted onsaid lead screw, one of the nut and the lead screw being linked to saidtransmissions means and the other of the nut and the lead screw beingdesigned to cooperate with said gearhead.

Advantageously, the lead screw, the nut and a part of the transmissionmeans are placed in the second chamber and the electric motor and thegearhead are placed in the first chamber, in such a way that moisture isconfined in a restricted area around the lead screw and in such a waythat the electric motor and the gearhead are not exposed to moisture andnot corroded. No specific measures against corrosion are needed.

Advantageously, the magnetic coupling device is designed to transmit themovement of the gearhead in the first chamber to one of the nut and thelead screw placed in the second chamber.

In one embodiment, the lead screw is a rotating lead screw designed tocooperate with the gearhead via the magnetic coupling device, and thenut is mounted on said lead screw and linked to the transmission means.More specifically, the first magnet is placed on a pin at the end of thegearhead and the second magnet is placed at the end of the lead screw.When the motor turns, the first magnet rotates and transmits rotation tothe second magnet that rotates the lead screw. The lead screw transmitsthe rotational movement into axial movement of the nut and finally thetransmission means.

In another preferred embodiment, the nut is a rotating nut designed tocooperate with the gearhead via the magnetic coupling device, and thelead screw, on which the rotating nut is mounted, is a linear lead screwlinked to the transmission means. More specifically, the first magnet isplaced on a pin at the end of the gearhead and the second magnet isplaced at the end of the rotating nut facing to the gearhead. When themotor turns, the first magnet rotates and transmits rotation to thesecond magnet that rotates the nut. The nut transmits the rotationalmovement into axial movement of the lead screw and finally thetransmission means.

Optionally a third magnet is mounted on a metal plate that shieldsmagnetic fields from the first magnet. This metal plate is the supportfor the first and third magnet.

This third magnet is used for the position sensing by using for exampletwo Hall sensors mounted at the front of the gearhead. With thisembodiment, the sensitivity of the Hall sensors is increased.

The transmission means may be mechanical, hydraulic, electromechanicalor pneumatic. Preferably, the transmission means may be a cable linkingone of the lead screw and the nut to the contractile element.

Advantageously, in the preferred embodiment comprising the rotating nutand the lead screw, the transmission means may be linked to the centerof the lead screw. Therefore there is no twist force between the screwand the nut, in such a way that the wear and the risk of blocking thenut decrease.

The cable may be protected by a coaxial sheath. The sheath can be madefor example of silicone, polyimide, PTFE composites (PTFE andfluoroethylkene polymers), pure PTFE, or other appropriate polymers. Thesheath can be additionally coated with silicone, if necessary. In otherembodiment, the cable may be surrounded by a silicone tube. Cables arewell known in surgery. As in the present invention one pulls on thecable to close the contractile element, a stiff cable is not required.Then bending up to 10 mm radius is possible. It could be a Teflon® cablein a Teflon® tube to reduce the friction. The cable could be woven outof several cables to be more flexible and to reduce risk in case ofcable break.

The cables can be made for example out of polyamide like Nylon®,polyether block amide, PTFE, or other appropriate polymers.Alternatively, other materials, as stainless steel or titanium, can beused. Surgeon is used to place cables in the human body.

The resting position of the contractile element of the structurecorresponds to a state in which any force is transmitted by thetransmitting means to the contractile element, and the activatedposition corresponds to a state in which a force has been transmitted insuch a way that the contractile element closes and constricts the organto be contracted.

In some embodiments, the contractile element is made out ofbiocompatible materials, preferably selected from the group consistingof silicone, PTFE composites (PTFE and fluoroethylkene polymers), purePTFE, polylactide (PLA)-polymer, polyurethane (PUR),Polymethylmethacrylate (PMMA), polyoxymethylene (POM), HDPE polyethyleneand LDPE polyethylene or combinations thereof. Other appropriatematerial as other polymers or metal can be used.

The contractile element of the contractile structure may have the formof an open ring to be placed around the organ or around a hollow part ofthe organ to be contracted, said ring having a moving part linked to thetransmitting means.

Preferably, the contractile element comprises a moving part linked tothe actuator and designed to move, when activated by the actuator,between the activated position and the resting position of thecontractile element.

Advantageously, the contractile element comprises a band which surroundsat least partially the organ to be contracted, and the transmissionmeans are designed to be linked to the band and to pull it, when thecontractile element is activated by the actuator, in such a way thatsaid contractile element reaches its activated position.

Preferably, at least a part of the transmission means is integrated insaid contractile element, such embodiment corresponding to means forreducing corrosion in the control unit. By this way, the contractileelement and the transmission means form only one member. As a part ofsaid transmission means is integrated in the contractile element, thereis neither opening nor interface between the contractile element and thetransmission means. Therefore, no body fluid can directly flow along thetransmission means into the control unit. Therefore, corrosion ofelectronic and mechanical parts in the control unit and in the actuatorcan be significantly reduced. Moreover, it will also prevent that partof the body fluid glue the cable.

Advantageously, the contractile element is a band in which thetransmission means, and more specifically the cable coming from theactuator are embedded.

The band may be a U-shaped band or a larger flat band. The U-shapeallows stabilizing the contractile element when closing whereas a largerflat band means that the contractile element is in contact with a largersurface contact area of the organ, which is more tissue friendly.

In one embodiment, the transmission cable is surrounded by a sleeve, asa Teflon® tube, which is in its turn embedded in a U-shaped band, madefor example of silicone.

In another embodiment, said sleeve is flat and is itself the larger bandin which the transmission cable is embedded. The band may be made ofTeflon®.

The sleeve is designed to act as a guiding spring allowing axialconstrict of the contractile element when it is pulled from resting oropen position to activated of close position. Such spring has anotheradvantage by the contractile element opening, only about 30 to 40% ofthe closing energy being needed. The sleeve may be advantageously madeof expandable Teflon®.

One end of the contractile element is linked to the transmission meanscoming from the actuator and its other end is free and designed tocooperate with locking means to fix this free end to the band.

In one embodiment, the locking means are a click mechanism. The free endof the band is made from PEEK, POM or similar biocompatible materialwhich is able to slide through a movable cover forming a locking membermade also from PEEK, POM or similar biocompatible material until theposition is reached where the band is surrounding the organ withoutapplying any surface pressure to the organ. In this position, the freeend of the band is clicked into the locking member. The free end of theband is protected with a silicone lip to guarantee that the organ is incontact only with soft silicone. The free end of the band is undercutallowing movable cover to be clicked. The cable may be fixed in the freeend by using for example a ball.

In another embodiment, the locking means are a snap mechanism. The freeend of the band is designed to cooperate with a grid provided on theother end of the band to close the contractile element.

Advantageously, a X-ray or CT marker may be incorporated into the bandof the contractile element in such a way that the position of saidcontractile element could be detected.

Advantageously, markers for circumference could be added in thecontractile element. This allows the physician to measure the organ andplace the band around the organ and moves it until the correspondingmarker is reached. Then the locking means are activated.

As a part of the transmission means is integrated in the contractileelement, the size of the contractile element is able to be adjusted tothe size of each individual organ with only one size of band. There isno need of some prefabricated sizes of band.

In some embodiments, the size of the band may be comprised between 3 cmand 15 cm in length, preferably between 3 cm and 12 cm in length, andbetween 3 mm and 15 mm in width, preferably between 3 mm and 12 mm inwidth.

The actuator may further comprise sensors designed to indicate theposition of the transmitting means or the force applied by the actuator.Preferably, such sensors are Hall sensors. Such sensors are preferablyplaced in the first or the third hermetically sealed chamber close tothe second magnets in the second chamber. In another preferred design,such sensors are placed in the first chamber at the front of thegearhead.

Advantageously, the source of energy has a volume less than 20 cm³,preferably less than 15 cm³ and most preferably less than 12 cm³.

Moreover, the ratio “current which is needed to maintain the contractileelement in its activated position and in its resting position/currentwhich is needed to change the position of the contractile element” isless than 1/500, preferably less than 1/800, and more preferably lessthan 1/1000. Preferably, the ratio “current which is needed to maintainthe contractile element in its activated position and in its restingposition/current which is needed to change the position of thecontractile element” is comprised between 1/20000 and 1/500, preferablybetween 1/14000 and 1/800, and more preferably between 1/8000 and1/1000.

Advantageously, the actuator comprises actuating means (preferably thescrew/nut system) designed in such a way that the energy consumption ofsaid medical device which is needed to change the position of thecontractile element and to move it between its activated position andits resting position is less than 2000 mAh/year and preferably less than1800 mAh/year and in such a way that the energy consumption of saidmedical device which is needed to maintain the contractile element inits activated position is less than 200 mAh/year for a continuouspressure applied on the organ by the contractile element, which is inits activated position, comprised between 0.1 N/cm² and 5 N/cm².Preferably, this pressure is applied alternatively through independentcontractile elements.

Preferably, said actuating means are designed in such a way that theenergy consumption of the medical device which is needed to change theposition of the contractile element is less than 1350 mAh/year and insuch a way that the energy consumption of said medical device which isneeded to maintain the contractile element in its activated position isless than 150 mAh/year for a continuous pressure applied on the organ bythe contractile element, which is in its activated position, comprisedbetween 0.3 N/cm² and 2.5 N/cm². Preferably, this pressure is appliedalternatively through independent contractile elements.

Advantageously, the current consumption of the medical device of theinvention which is needed to change the position (moving between theactivated position and the resting position) of the contractile elementfor five years is comprised between 350 mAh and 9000 mAh, preferablybetween 350 mAh and 6750 mAh, and the current consumption of saidmedical device which is needed to maintain the contractile element inits activated position is comprised between 75 mAh and 1000 mAh for acontinuous pressure applied on the organ by the contractile element,which is in its activated position, comprised between 0.1 N/cm² and 5N/cm², preferably between 0.3 N/cm² and 2.5 N/cm². Preferably, thispressure is applied alternatively through independent contractileelements.

The source of energy can be implantable or placed outside the body ofthe patient.

In one embodiment, the actuator and its control unit, and the source ofenergy are implantable and are placed in the same closed box, separatedfrom the contractile structure or from the contractile elements.

In a preferred embodiment, the control unit and the source of energy areseparated in two boxes (control unit and power supply unit) andconnected with an electric cable, which should be easily detachable. Adirect current (DC) can be used between the power supply unit and thecontrol unit. In a preferred embodiment, one uses means for providing acurrent conversion DC/AC (alternative current)/DC between the powersupply unit and the control unit. Such embodiment allows to reduce thecorrosion of the cables connecting the power supply unit and the controlunit. Therefore the means for providing a current conversion DC/AC/DCbetween the power supply unit and the control unit are also means forreducing corrosion of the medical device.

In other embodiments, the actuator and its control unit is implantableand the source of energy is placed outside the body of the patient. Insome embodiments, the source of energy comprises at least oneimplantable rechargeable battery with an implantable antenna and anexternal battery. Such implantable battery is for example a Lithium-Ionor Lithium Polymer rechargeable battery commercialized by GreatBatch andothers. The energy transfer system that is needed to recharge thebattery, is preferably through wireless connection. Such system cancomprise a recharge unit, as a belt, comprising an external battery. Thepatient should wear the recharge unit for a number of hours to rechargethe implanted battery. The energy should be transmitted wireless to theimplanted battery via appropriate antenna. The system can also comprisea cradle for charging the recharge unit. Charging can be performedthrough a wired or metal contact connection. The battery providessufficient energy for at least 1 month operation of the medical device.Recharge time is less than 6 hours. In another preferred embodiment, thesource of energy is at least one implantable primary (i.e.non-rechargeable) battery, having advantageously a lifetime of at least4 years for a volume of 3.7 cm³ (in total 7.4 cm³ if two batteries areused). The battery may be a lithium-manganese dioxide battery.

The battery volume and weight are crucial for implantable devices.Therefore a high power density is needed. Larger batteries with lowerpower density exist. But if these batteries are too big and heavy, theycannot be implanted. The devices would become too large and e.g. visibleunder the skin. Further it is not always possible to fix the device inthe body. Therefore there is a risk of implant movement due to highweight of the device. Heavy devices could be not comfortable for thepatient. Moreover, too large and heavy batteries could be the reason toexclude a device for a particular therapy.

The features of the battery depend on the application of the artificialstructure, on the pressure to be applied, on the number of contractileelements to activate, and how often the patient opens and closes thecontractile structure.

In the present invention, when energy is provided to the electromotor,this energy may be transmitted, via the magnetic coupling device whichis placed between the electromotor and the lead screw/nut system, to oneof the lead screw and the nut, which converts its rotation movement to alateral or axial movement of the other of the lead screw and the nut.When the nut or the lead screw moves axially, it pulls or pushes thecable to close or open the contractile element. No extra releasemechanism is required. No or minimal energy is needed to maintain thecontractile element in its activated position due to the self-lockinglead screw design, which means that the maximum pressure on the organ ismaintained with minimal energy consumption. Moreover, no or minimalenergy is needed to maintain the contractile element in its restingposition due also to the self-locking lead screw design. In the casecorresponding to minimal energy consumption, only a few electroniccomponents on the printed circuit board are permanently powered, mainlyfor communication purpose with the remote controls.

Most energy is needed for just a few seconds to move the screw/nutsystem and close and open the contractile element which also providessignificant reduction of the power consumption that allows a significantincrease in the battery life time.

The cycle of a contractile element of the invention is that no energy isprovided to maintain the contractile element in its resting position,some energy is needed for just a few seconds to move the nut and closethe contractile element until its activated position, then no energy isprovided to maintain the contractile element in its activated position,and then some energy is needed for just a few seconds to move the nutand open the contractile element until its resting position. Therefore,no continuous energy is needed in such a way that the contractileelement is maintained in its activated or resting position. The totalenergy consumption is then very low.

Moreover, due to the use of a spring sleeve in which the cable isinserted, the device of the invention needs only about 30 to 40% of theclosing energy to open the contractile element.

With such lower energy consumption, which was never disclosed in theprior part, the operation time of the battery used as source of energyis comprised between 1 month and 10 years, preferably between 1 year and10 years, and more preferably between 2 years and 8 years, optimally 5years, for a battery having a volume of 3 cm³ to 20 cm³.

The medical device of the invention allows therefore the use of aprimary battery placed inside the body of the patient, which is to bechanged only several years after its implantation, optimally 5 years fora battery having a volume of 3 cm³ to 20 cm³. Therefore the medicaldevice of the invention need no accumulator or rechargeable battery,which is an advantage compared to the devices of the prior art.

Moreover, the motor, the gear ratio and the lead screw/nut system havebeen chosen in such a way that the travel time needed by the nut formoving along the lead screw and the lead screw moving in case ofrotation nut between the resting position and the activated position iscomprised between 0.2 s and 90 s, for a travel of the nut comprisedbetween 2 mm and 50 mm, preferably between 3 mm and 15 mm. Preferably,the travel time needed by the nut or the lead screw, respectively formoving between the resting position and the activated position iscomprised between 0.4 s and 60 s, more preferably between 0.5 s and 10s, and more preferably between 0.5 s and 5 s for a travel of the nut orthe lead screw respectively comprised between 2 mm and 50 mm, preferablybetween 3 mm and 15 mm.

The time for opening or closing the contractile element could bedifferent and depends on the material of the contractile element.

The appropriate electromotor is commercialized for example by MaxonMotor AG, Faulhaber or Portescap. Preferably, the gear ratio iscomprised between 4 and 64, and preferably between 12 and 64. The leadscrew has a pitch comprised between 0.2 mm and 3 mm, preferably between0.3 mm and 2 mm, and more preferably between 0.4 mm and 1 mm and aneffective diameter comprised between 1 mm and 4 mm. Leadscrews withmetric threads, for example with a thread angle of 60°, could be used.Preferably, the leadscrew has trapezoidal threads, for example with athread angle of 30°. This configuration allows to obtain better yield.

The following strategies have been worked out to reach a high efficientand power saving device.

First, the requirements for battery system in implant should be a veryhigh power density, low self discharge rates, low serial impedance formedium pulse power demands, negligible voltage delays, guaranteed ratedcapacity, and reliable definition of end of life (EOL) condition.

Moreover, the system concept of electronic design shall provide powersaving modes (e.g. switch-off unused parts, minimize current consumptionof permanent powered parts), consume electrical power directly frombattery, minimize serial impedances in the power paths, ensure areliable detection of battery EOL condition, and minimize currentconsumption during idle mode.

The system concept of mechanical design shall provide actuator systemwhich ensures high efficiency, low starting voltages and simple control,ensure no permanent current consumption, and provide fast and low powerposition control.

The system concept of wireless communication design shall meet ultralow-power design challenges and ensure low error rates.

The key points to get a high efficient and power saving medical deviceof the invention were:

-   -   two implantable primary batteries (non-rechargeable); chemistry:        LithiumManganese Dioxide for example    -   ultra low power consumption (<6 μA) during idle mode; only few        active parts are permanently powered    -   design provides several power saving modes (stop mode+several        intermitted modes)    -   wireless communication based on medical implant communication        service (MICS)—duty cycle sniffing for wake-up    -   actuator system based on high performance DC motors, combined        with gear box and lead screw deliverable as a compact unit    -   gear box with self-retention ensures powerless hold    -   detection of lead nut position (travel measurement) with a Hall        sensor for precise measurements and lowest current consumption        due to the self-locking lead screw design as described above.

The medical device of the invention can comprise only one actuator, thetransmission means being designed to transmit the forces induced by theactuator to each of the contractile elements of the structure.

In other embodiments, the medical device can comprise several actuators,each actuator being associated, via appropriate transmission means, toone or several contractile elements.

The artificial contractile structure may be a structure comprisingseparate contractile elements described above or linked by a support.

In some embodiments, the artificial contractile structure may compriseat least two contractile elements, which can be independent ordistributed along a support, in order to be able to reduce the volume ofthe organ to be contracted in at least two distinct regions of saidorgan. The device may comprise at least two actuators respectivelylinked to their corresponding contractile element by their correspondingtransmitting means. Each contractile element is able to contract aportion of the organ and to be activated or in a resting positionindependently of the position of the other contractile elements.

If the structure comprises several contractile elements, saidcontractile elements can be designed in such a way that each contractileelement is connected to an adjacent contractile element, while remainingflexible one with respect to the other. That means that a contractileelement and its adjacent contractile element are physically linked orconnected to each other, directly or indirectly, by an appropriateconnecting element, allowing one to obtain a compromise between thestiffness and the flexibility of the structure. This structure allowsapplying to minimal pressure to the tissues avoiding tissue necrosis anddamage. Moreover, this structure allows optimal pressure control andimplantation of the structure by surgeons, by having a single-piecedevice which is adaptive to the natural flexibility of the urethra whileremaining semi-rigid so that the structure stays in place and thepressure of each contractile element can be optimally synchronized.

In some embodiments, the artificial contractile structure may furthercomprise a first flexible connecting element designed to link eachcontractile element to an adjacent contractile element, said connectingelement being made out of elastic biocompatible material for keepingsaid contractile elements flexible one with respect to the other. Suchfirst flexible connecting element may be fastened directly to thecontractile elements.

More particularly, in some embodiments, said first flexible connectingelement is able to keep the contractile elements in longitudinalposition while allowing a rotational movement of each contractileelement one with respect to the other.

In other embodiments, the artificial contractile structure may comprisetwo merged contractile elements both elements working independently (oneis open while the other is closed). Such contractile elements may beconnected by a band of silicone as a flexible connecting element,allowing both elements working independently from each other. Suchsilicone band has also the advantage that the contractile elementscannot overlap over time.

In other embodiments, two adjacent transmissions means are merged insuch a way that the two corresponding adjacent contractile elements areindirectly connected.

In some embodiments, the medical device further comprises at least onesecond connecting element designed to merge the adjacent transmissionsmeans of two adjacent contractile elements, in such a way that saidadjacent contractile elements are indirectly connected via theirtransmissions means, and more particularly via the cables linking theactuators to the adjacent contractile elements. Such second connectingelement may be bars or other similar connecting elements used to mergesaid two adjacent transmission means. In other embodiments, thetransmissions means may be merged by overmolding. In this manner, thecontractile elements may be kept in longitudinal position while allowinga rotational movement of each contractile element one with respect tothe other.

Advantageously, each contractile element is flexible so that it has thefreedom to move longitudinally no more than 5 mm to each direction,preferably no more than 3 mm to each direction, and more preferably nomore than 1 mm to each direction from an adjacent contractile element,and so that it can move according to a transversal rotation no more than30°, to each side, preferably no more than 20° to each side from anadjacent contractile element, allowing the most flexibility andindependence of each contractile element from its adjacent contractileelements preventing a peristaltic movement of the whole device along theurethra and allowing optimal synchronization of the contractileelements.

In some embodiments, the control unit may be adapted to pulsatory andalternately activate each contractile element, independently from eachother. The actuators are preferably controlled by the same control unit.

In some embodiments, the medical device may further be combined with adevice that signals the patient that the contractile structure will opensoon, e.g. within next five minutes. This embodiment is preferred if theorgan is the bladder, so that the patient has time enough to go to thetoilet. The signaling device can be for example a vibration alarm or aLED. The medical device may also further comprise an automated closingfeature that the device automatically closes after e.g. 3 min. This hasthe advantage in case the patient forgets to close.

In the invention, the contractile structure is placed around an organ tobe contracted or is placed on (or close to) an organ so that a localpressure is applied to such organ. It may comprise one or morecontractile elements disposed around the organ.

A medical device of the invention that has one or more contractileelements placed on an organ (so that a local pressure on such organ isachieved, preferably in a pulsatory manner) may be easier to implant forsurgeons, because delicate and/or lengthy surgery around the organ isavoided. In the field of incontinence, this device may however be lessconvenient for full control of incontinence compared to a device wherebythe contractile structure is around the urethra. Such medical device(that has one or more contractile elements on an organ) is howeversuperior to the commercial slings used to control urinary incontinencewhich have lower success rates (see Retropubic versus TransobturatorMidurethral Slings for Stress Incontinence, Holly E. Richter et al. TheNew England Journal of Medecine, 2010; 362:2066-79). Therefore thecontractile structure of the medical device of the invention may bedesigned as a classical sling in terms of shape and dimensions so that acontrolled (by the patient) local pressure is applied on the urethra,therefore maximizing control of incontinence. Hereby such device isdefined as an “active sling”.

This active sling may not be limited by the embodiments of the presentinvention, meaning that contractile element may be activatedmechanically by hydraulic or pneumatic means as described for in theprior art AMS800 device. Preferably, however a source of energy forpowering is used, but the energy consumption of said medical device maybe even lower than 50 mAh/year for a pressure applied by the contractileelement on the organ comprised between 0.1 N/cm² and 5 N/cm², for abattery having a volume between 3 cm³ and 20 cm³. Interestingly even asmall pressure on the urethra that is managed by an active sling willimprove control of incontinence compared to traditional slings.

Preferably, this active sling is adapted to be placed, at leastpartially, in a female or male patient in one of several locations,i.e., below the pubis bone, so as to lift the urethra from a point belowthe pubis bone when the patient is standing, into the pubis bone, so asto lift the urethra from a point attached to the pubis bone of thepatient, or above the pubis bone of the patient, so as to lift theurethra from a point above the pubis bone when the patient is standing.

The urethra is lifted by reducing the length of the u-shaped traditionalsling. Normally the device forms a loop and the adjustment changes thelength of the loop to lift the urethra. The loop can have any shape orform that can be used to lift the urethra when placed inside the loop,when implanted. The device forms a loop that is placed around stabletissue. The loop holds up the urethra, when placed inside the loop, whenimplanted. Preferably, the interconnecting part is a band or a thread,or a plurality of bands or threads connected to each other to lift theurethra.

The control unit and/or power supply unit includes electronics andsoftware designed to:

-   -   control and adjust the actuator generating the force transmitted        to the contractile element    -   provide control of the actuator from outside the body through        wireless connection    -   optionally recharge the internal battery through wireless        connection    -   control the status of the battery    -   provide test and diagnosis support for health care professionals    -   handling of alarm conditions and exceptions.

The control unit comprises a microprocessor that distributes current toactuators so that they activate the contractile elements pulsatory, atthe required pressure and at the required frequency.

As described above, said electronics is placed in the first or thirdhermetically sealed chamber of the control unit, and preferably in thethird chamber, separated from the motor and its gearhead.

The microprocessor can be adjusted via remote control individually foreach patient regarding pressure and frequency of opening and closing.

Ideally these adjustments can be done after implantationtranscutaneously, preferably by a medicinal physician in order tooptimize control of volume reduction (such as incontinence leaking).Readjustments can be performed at any time during the life time of thedevice using a remote control, as described below.

The number of contractile elements to contract can be adapted to therequired pressure to apply on the organ. For example, in the case ofurinary sphincter, the number of contractile elements to open and closecan be adapted to the abdominal pressure.

The pressure of the structure on the region of the organ to becontracted may be comprised between 0.1 N/cm² and 5 N/cm², andpreferably between 0.3 N/cm² and 2.5 N/cm².

In a preferred embodiment, the device of the invention comprises:

-   -   i) an artificial contractile structure implantable into the        human body and comprising one or more contractile elements able        to be activated by an actuator as described above,    -   ii) at least one implantable actuator which upon activation will        induce a contraction of the contractile elements, such as the        actuators described above,    -   wherein the actuator and the contractile elements are designed        so that the pressure, applied on the organ to be contracted, is        comprised between 0.1 N/cm² and 5 N/cm², and preferably between        0.3 N/cm² and 2.5 N/cm² during a period comprised between 30        seconds and 90 minutes, preferably between 30 seconds and 60        minutes, more preferably between 30 seconds and 45 minutes, and        more preferably between 10 minutes and 30 minutes.

Each contractile element is preferably activated or deactivated severaltimes a day, and most preferably several times an hour. The contractileelements may be activated, in a pulsating and alternating manner, apressure on an organ to be contracted during a period comprised between30 seconds and 90 minutes, preferably between 30 seconds and 60 minutes,more preferably between 30 seconds and 45 minutes, and more preferablybetween 10 minutes and 30 minutes. Preferably, the strength is such thatthe different regions of the organ are completely closed in a pulsatingand alternating manner. The relaxation time is dependent on the numberof regions which are to be contracted by the independent contractileelements.

If the artificial structure is adapted to contract for example fourregions of an organ, and if only one contractile element is activated atthe same time, each contractile element can be activated during oneminute and deactivated during three minutes in an alternating manner. Inanother embodiment, each contractile element can be activated duringfive minutes and deactivated during fifteen minutes in an alternatingmanner. If the structure is adapted to contract three regions of anorgan, each contractile element can be activated during one minute anddeactivated during two minutes in an alternating manner. If thestructure is adapted to contract two regions of an organ, it comprisestwo contractile elements, which can be activated during 30 minutes anddeactivated during 30 minutes in an alternating manner.

The activation of each contractile element can be random or sequential.

Only one of the contractile elements or several contractile elements canbe contracted at the same time. In other embodiments, one contractileelement can remain contracted or closed whereas another contractileelement is contracted or closed.

Advantageously, the medical device comprises a control unit which isdesigned so that at least two contractile elements are able to bemaintained in the same position at the same time. This feature of themedical device may be used separately or in combination with anyone ofthe features of the medical device described above.

Preferably, at least two contractile elements are able to be actuatedpulsatory and alternately independently from each other and also to bemaintained in the same position at the same time. More preferably, atleast two contractile elements are able to be maintained in theiractivated position at the same time, preferably for sport activities ofa patient.

If the patient wishes to do sport, several or all the contractileelements may be closed in such a way that the pressure, which is appliedon the organ to be contracted, is increased for a certain time,typically 1 h (so called sports mode). After that time the system goesback into the alternately activation controlled by the control unit. Toavoid tissue damage sports mode cannot be activated more than twice in arow and not more than maximum 3 hours a day.

Advantageously, the control unit is designed so that at least twocontractile elements are able to be maintained in their resting positionat the same time, preferably for sleep activities of a patient.

During the night, several or all the contractile elements may bemaintained in a resting position, without any contraction in such a waythat the energy consumption is reduced.

All these embodiments are obtained by means of an adequate control unit.Said control unit is designed to allow an adjustment of the pressure ofthe contractile structure on the organ according to the patient's need,by adjusting the force generated by the actuator and the frequency thecontractile structures are acting. Advantage is that the physician cancustomize the optimal pressure of the contractile structure to sideeffects on the organs, for example by means of a magnet placed aroundthe device. The parameters of the control unit and also of the actuatorcan be adjusted by the physician after the implantation of the deviceduring the postoperative consultations.

The control of the contractile structure and more especially its openingcan be achieved, by the physician or the patient himself, by a manualcontrol of the control unit by means of a remote control to open andclose the urethra. The remote control is preferably wireless. For thephysician, the remote control can be designed to enable adjustments ofthe medical device (activation force, parameters of the pulsatory andalternately activation, test and diagnosis mode). An optical signaland/or vibration and or acoustic signal may be provided in order to showthe patient the level of the battery status. Two different remotecontrols can be provided: a simple remote control for the patient and anadvanced remote control for the healthcare professionals. The patientgets a simple remote control to open and close the contractile structureand to get some information like battery status and device status. Thehealthcare professionals have an advanced remote control that inaddition allows to readjust the pressure and frequency, move the deviceinto the examination mode as described below (motor will move typically5 mm in the opposite direction of closing the contractile structure)reading implant parameters.

Advantageously, the medical device of the invention further comprisessafety means designed to change automatically the position of thecontractile element.

This feature of this medical device may be used separately or incombination with anyone of the features of the medical device describedabove.

Advantageously, said safety means are designed to move automatically thecontractile element from its activated position into its restingposition. More particularly, said safety means are designed to moveautomatically the contractile element from its activated position intoits resting position if the pressure applied on the organ is higher thana preset pressure or if the power of the source of energy is less than apreset power.

Advantageously, said safety means are designed to move automatically thecontractile element from its resting position into its activatedposition for example if the time for which the organ is not constrictedis higher than a preset time.

For emergency, the control unit may be controlled by means of a switchplaced under the skin, which is activated by pressure on one or severalbuttons. Preferably, the switch comprises several buttons and thesequence for pressing the buttons is predetermined in order to avoidaccidental opening of the structure.

Another alternative for safety is a strong magnet used outside the bodyfor moving on the skin to activate the lead screw/nut system, to openthe contractile element in case of a mechanical failure (e.g. motorblocked).

Another alternative for safety is the automatic opening of thecontractile elements after reaching a certain force (typically 5N) orpressure.

In other embodiments, the control of the contractile structure and moreespecially its opening can be achieved, by the physician or the patienthimself, by a manual control of the contractile elements themselves bymeans of a releasing device designed to manually open the contractilestructure. Such releasing device can be used if the patient lost theremote control or if a surgeon wishes to open the structure toendoscopically examine the patient or if a kidney stone has to beremoved. This corresponds to the examination mode (motor will movetypically 5 mm in the opposite direction of closing the contractilestructure to totally open the contractile structure) allowing theexamination with an endoscope without risk of damage of the urethra.

Advantageously, the closed structure of the invention has a diametercomprised between 8 mm and 35 mm. The dimensions of the open structureare such that, when the contractile element(s) of the structure is/arefully open, the surgeon can move an endoscope through the lumen of theurethra/rectum in order to endoscopically examine the patient. In thesame way, the dimensions of the open structure are such that, when thecontractile elements of the structure are fully open, kidney stoneremoval is possible.

Preferably, each contractile element is separated from an adjacentcontractile element no less than 1 mm to 2 cm, preferably 2 mm to 1 cm,more preferably 2 mm to 8 mm, for avoiding over-compression.

Preferably, the structure of the invention may be comprise between 2 and8 contractile elements, so that it makes an overall length comprisedbetween 20 mm and 50 mm.

The present invention relates also to a medical device comprising:

-   -   an artificial contractile structure comprising at least one        contractile element adapted to contract an organ, in such way        that said contractile element is in a resting or in an activated        position, the activated position being defined with said        contractile element constricting the organ and the resting        position being defined with said contractile element not        constricting the organ,    -   at least one actuator comprising at least one electromotor and        transmission means linked to the contractile element and        designed to transmit to the contractile element a force induced        by said electromotor,    -   at least one control unit comprising and controlling said        actuator,    -   at least one source of energy for powering said actuator.

According to the invention, said actuator comprises an internal magneticcoupling device designed to transmit to the contractile element a forceinduced by the electromotor.

Said actuator comprises at least an electric motor, a gearhead connectedto said electric motor, a lead screw and a nut mounted on said leadscrew, one of the nut and the lead screw being linked to saidtransmission means and the other of the nut and the lead screw beingdesigned to cooperate with said gearhead.

The magnetic coupling device comprises a first magnet designed tocooperate with the gearhead, a second magnet designed to cooperate withone of the nut and the lead screw, and optionally a third magnet whichis mounted on a plate supporting the first magnet. The magnets areimplanted in the body of the patient.

The actuator further comprises sensors designed to indicate the positionof the transmission means.

Advantageously, the sensors are Hall sensors and are placed at thegearhead. This allows to increase the sensitivity of the Hall sensors.

EXAMPLES

Referring to FIG. 1, one embodiment of the medical device of theinvention, used to treat urinary incontinence, comprises two adjacentcontractile elements 100 designed to surround partially a hollow part ofthe urethra. The contractile elements 100 are indirectly connected byusing bars 102, said bars being connecting elements fixed around thetransmission means and used to merge said two adjacent transmissionmeans, i.e. the two adjacent cables which are inserted in Teflon® tubes104 which are covered with silicone (silicone tube or silicone coating).

The contractile element 100 comprises a U-shaped band 106 designed tosurround at least one time the hollow part of the organ to becontracted. The band 106 is made of silicone, PTFE, PLA, PUR, PMMA,(POM), HDPE LDPE or combination thereof to reduce the friction when theband wraps closely around the organ.

At shown by FIG. 2, the band 106 comprises a first end 106 a, in whichthe tube 104 comprising the cable, is integrated and a second end 106 b,which is free. This free end 106 b is made from PEEK, POM or similarbiocompatible material which is able to slide through a movable coveracting as a locking member 108 of a click mechanism and made also fromPEEK, POM or similar biocompatible material until the position isreached where the band 106 is surrounding the organ without applying anysurface pressure to the organ. In this position, the free end 106 b ofthe band 106 is clicked into the locking member 108. The free end 106 bof the band 106 is protected with a silicone lip 110 to guarantee thatthe organ is in contact only with soft silicone.

In another embodiment as shown by FIG. 3, the contractile element 100comprises locking means which are a snap mechanism. The free end 106 bof the U-shaped band 106 is designed to cooperate with a grid 107provided on the other end 106 a of the band 106 to close the contractileelement 100.

The medical device comprises also two actuators placed in a box 112 awayfrom the organ to be contracted. Each actuator is linked to thecorresponding contractile element 100 by the corresponding cable in thecorresponding tube 104.

A control unit 114 is used to control and activate the contractileelement 100 shown in FIGS. 1 and 2. The control unit 114 is placed in abox 112 made of titanium.

FIG. 4 shows one of the actuators 116, said actuator having anelectromotor comprising an electric motor 118, a gearhead 120 connectedto said motor 118, a lead screw 124 and a rotating nut 122 mounted onsaid lead screw 124. The nut 122 is a hollow cylinder, in which the leadscrew 124 is able to move according to an axial movement. Ball bearings123 are provided for improving the rotation of the nut 122. The tube 104and its cable are attached to the center of the lead screw 124, alongthe lead screw axis. The end of the tube 104 and the cable, the leadscrew 124 and the nut 122 are placed in a second chamber 126, which isnot hermetically sealed. The motor 118 and the gearhead 120 are placedin a first chamber 128, which is made of titanium and which ishermetically sealed with the second chamber 126 by using the thintitanium wall 130 of the second chamber 126 as a hermetic seal. A firstmagnet 132 is placed in the first chamber 128 and a second magnet 134 isplaced in the second chamber 126, face to face on each side of thehermetic seal 130.

The second magnet 134 is placed at the end of the rotating nut 122facing to the gearhead 120 and the first magnet 132 is placed on a pinat the end of the gearhead 120. When the motor 118 turns, the firstmagnet 132 rotates and transmits rotation to the second magnet 134 thatrotates the nut 122. The nut 122 transmits the rotational movement intoaxial movement of the lead screw 124 and finally the cable in the tube104 that transmits the force to the corresponding contractile element100 to close or open it.

The cable is woven out of several bars or one single bar and is made ofstainless steel, titanium or polymer and inserted in the tube 104 madeof Teflon®.

The control unit 114 comprises also a printed circuit board to controlthe actuators 116 and a position Hall sensor which are placed outsidethe second chamber 126 close to the second magnet 134.

In another preferred embodiment as shown by FIGS. 6 and 7, a thirdmagnet 135 is mounted on a metal plate 137 that shields magnetic fieldsfrom the first magnet 132. This metal plate 137 is the support for thefirst 132 and third 135 magnet. This third magnet 135 is used for theposition sensing by using for example two Hall sensors 139 which areplaced in a third chamber at the front of the gearhead 120. The Hallsensors 139 are mounted on a flex PCB 141.

As shown by FIG. 1, the control unit 114 is separated from the energysource. The energy source is in the power supply unit 140 that isconnected to the control unit 114 by two electric cables 142, which areeasily detachable by using connectors 144. The energy source comprisestwo implantable primary (i.e. non-rechargeable) batteries, each having alifetime of at least 4 years for a volume of 3.7 cm³. In another notshown embodiment, the batteries may be in sequence instead of inparallel. Therefore, only one electric cable and only one connector canbe used.

In case of power loss the control unit comprises a capacitor which hasenough energy stored to apply to the electromotors and to open thecontractile elements 100.

Almost no energy is needed to maintain the contractile element 100 inits activated position due to the self-locking characteristics of thelead screw/nut combination. Only a few electronic components arepermanently powered.

The control unit is adapted to distribute current to each actuator,preferably in order to pulsatory and alternately contract thecontractile elements 100.

In this case, there are several gates which can be independently,pulsatory and alternately activated in order to contract one or theother region around which the contractile elements 100 have been placed,in a pulsating and alternating manner. This allows an alternatecontraction along the urethra, several times an hour. Such aconfiguration avoids stressing of the underlying tissue followed byerosion and necrosis.

The control unit is designed to activate at least one actuator andtherefore to activate at least one contractile element so that at leastone region of the urethra is closed to avoid incontinence. The patientdeactivates the device if necessary, so that each actuator isinactivated to open each region of the hollow part of the urethra,allowing the passage of the urine.

There are also means for opening on demand said artificial contractilestructure, used by the physician or the patient himself to inactivatethe actuators and open the contractile elements.

The device can further comprise sensing means selected from pressure,and force sensing means.

Obviously, the device of the invention can be used with a control unitadapted to drive the contraction of the contractile elements, on demand,without pulsatory and alternately contracting said contractile elements.

The operating time of the medical device as shown by FIG. 1 was testedfor different travels of the lead screw 124 and for different cycletimes.

The travel is the distance covered by the lead screw 124 in such a waythat the contractile element 100 moves between its resting and activatedpositions. A cycle time comprises movement of the lead screw for closingthe contractile element, time for which the contractile element isclosed, movement of the lead screw for opening the contractile elementand time for which the contractile element is opened.

The travels were 8 mm and 4 mm. The cycle times were 10 minutes, 20minutes and 30 minutes.

The electromotor comprised the motor 0816006S from Faulhaber, lead screwpitch is 2.29 mm and the diameter is 2.00 mm; gear ratio is 9:1.

The control unit comprises as source of energy two primary batteries of1.1 Ah, with an assumed shelf life of 1 year, for a volume of 3.7 cm³each.

The pressure applied by the contractile element on the organ was 1.5 N.

The results are shown by FIG. 5, which represents the cycle time as afunction of the operating time for different travels for a travel of thelead screw of 8 mm (curve A), and a travel of 4 mm (curve B). FIG. 5shows that the medical device of the invention allows to use primarybatteries enabling to obtain an operating time of 1.8 years to 7.5years.

Moreover, such a medical device allows applying minimal pressure to thetissues thereby avoiding tissue necrosis and damage, even if eachcontractile element applies a pressure at a frequency of 30 to 45minutes alternately with the other contractile elements. That means thatevery contractile element is closed for 30 to 45 minutes alternatelywith the other contractile elements. A device as AMS 800 shows erosionbecause the device is closed for about 6 to 8 hours per night and duringthe day for about 4 hours, assuming that the patient goes every 4 h tothe toilet.

The invention claimed is:
 1. A medical device comprising: an artificialcontractile structure comprising at least one contractile elementadapted to contract an organ, in such way that said contractile elementis in a resting or in an activated position, the activated positionbeing defined with said contractile element constricting the organ andthe resting position being defined with said contractile element notconstricting the organ, at least one actuator, at least one control unitcomprising and controlling said actuator, at least one source of energyfor powering said actuator, wherein said actuator is designed toactivate said contractile structure in such a way that the ratio“current which is needed to maintain the contractile element in itsactivated position and in its resting position/current which is neededto move the contractile element between its activated position and itsresting position” is less than 1/500, means for reducing corrosion ofthe medical device, safety means designed to change automatically theposition of the contractile element, wherein said safety means aredesigned to move automatically the contractile element from itsactivated position into its resting position if the power of the sourceof energy is less than a preset power, and wherein the at least onesource of energy is an implantable battery in a power supply unitremovably connected to the at least one control unit.
 2. The medicaldevice according to claim 1, wherein the ratio “current which is neededto maintain the contractile element in its activated position and in itsresting position/current which is needed to move the contractile elementbetween its activated position and its resting position” is less than1/800.
 3. The medical device according to claim 2, wherein the ratio“current which is needed to maintain the contractile element in itsactivated position and in its resting position / current which is neededto move the contractile element between its activated position and itsresting position” is less than 1/1000.
 4. The medical device accordingto claim 1, wherein said actuator comprises at least one electromotorand transmission means linked to the contractile element and designed totransmit to the contractile element a force induced by saidelectromotor.
 5. The medical device according to claim 4, wherein saidactuator further comprises a magnetic coupling device designed totransmit to the contractile element a force induced by the electromotor.6. The medical device according to claim 5, wherein said magneticcoupling device is placed at the end of a gearhead of the electromotor.7. The medical device according to claim 4, wherein said actuatorcomprises at least an electric motor, a gearhead connected to saidelectric motor, a lead screw and a nut mounted on said lead screw, oneof the nut and the lead screw being linked to said transmission meansand the other of the nut and the lead screw being designed to cooperatewith said gearhead.
 8. The medical device according to claim 4, whereinsaid transmission means are mechanical, hydraulic, electromechanical orpneumatic.
 9. The medical device according to claim 8, wherein thetransmission means are a cable linking one of the nut and the lead screwto the contractile element.
 10. The medical device according to claim 5,wherein means for reducing corrosion of the medical device comprisemeans for reducing corrosion in the control unit which consist in such away that the control unit comprises at least one first chamber, which ishermetically sealed and contains elements of the control unit which arethe most sensitive to moisture, and on its side facing the contractileelement, at least one second chamber which is not hermetically sealed.11. The medical device according to claim 10, wherein the lead screw,the nut and a part of the transmission means are placed in the secondchamber and wherein the electric motor and the gearhead are placed inthe first chamber.
 12. The medical device according to claim 11, whereinthe magnetic coupling device is designed to transmit the movement of thegearhead in the first chamber to one of the nut and the lead screwplaced in the second chamber.
 13. The medical device according to claim12, wherein the magnetic coupling device comprises either two magnets,in which a first magnet designed to cooperate with the gearhead, and asecond magnet designed to cooperate with one of the nut and the leadscrew, or three magnets, in which a first magnet designed to cooperatewith the gearhead, a second magnet designed to cooperate with one of thenut and the lead screw, and a third magnet which is mounted on a platesupporting the first magnet.
 14. The medical device according to claim12, wherein the nut is a rotating nut designed to cooperate with thegearhead via the magnetic coupling device, and wherein the lead screw isa linear lead screw linked to the transmission means.
 15. The medicaldevice according to claim 4, wherein the actuator further comprisessensors designed to indicate the position of the transmission means. 16.The medical device according to claim 15, wherein the sensors are placedat the gearhead.
 17. The medical device according to claim 1, whereinthe contractile element comprises a moving part linked to the actuatorand designed to move, when activated by the actuator, between theactivated position and the resting position of the contractile element.18. The medical device according to claim 17, wherein the contractileelement comprises a band which surrounds at least partially the organ tobe contracted, and wherein the transmission means are designed to belinked to the band and to pull it, when the contractile element isactivated by the actuator, in such a way that said contractile elementreaches its activated position.
 19. The medical device according toclaim 10, wherein means for reducing corrosion in the control unitconsist in such a way that at least a part of the transmission means isintegrated in the contractile element allowing to reduce corrosion inthe control unit.
 20. The medical device according to claim 1, whereinthe ratio “current which is needed to maintain the contractile elementin its activated position and in its resting position/current which isneeded to move the contractile element between its activated positionand its resting position” is comprised between 1/20000 and 1/500. 21.The medical device according to claim 1, wherein the energy consumptionof said medical device is less than 2000 mAh/year for a continuouspressure applied on the organ which is less than 5 N/cm².
 22. Themedical device according to claim 21, wherein the energy consumption ofthe medical device is less than 1800 mAh/year for a continuous pressureapplied on the organ which is less than 2.5 N/cm².
 23. The medicaldevice according to claim 1, wherein said source of energy has a volumeless than 20 cm³.
 24. The medical device according to claim 1, whereinthe source of energy is selected to have an operation time comprisedbetween 2 months and 10 years.
 25. The medical device according to claim1, wherein the artificial contractile structure comprises at least twocontractile elements in order to be able to reduce the volume of theorgan to be contracted in at least two distinct regions of the organ.26. The medical device according to claim 25, wherein it furthercomprises at least two actuators respectively linked to theircorresponding contractile element by their corresponding transmittingmeans.
 27. The medical device according to claim 25, wherein eachcontractile element is connected to an adjacent contractile element,while remaining flexible one with respect to the other.
 28. The medicaldevice according to claim 27, wherein the artificial contractilestructure further comprises a first flexible connecting element designedto link each contractile element to an adjacent contractile element,said first connecting element being made out of elastic biocompatiblematerial for keeping said contractile elements flexible one with respectto the other.
 29. The medical device according to claim 25, wherein twoadjacent transmissions means are merged in such a way that the twocorresponding adjacent contractile elements are indirectly connected.30. The medical device according to claim 29, wherein the medical devicefurther comprises at least one second connecting element designed tomerge the adjacent transmission means of two adjacent contractileelements.
 31. The medical device according to claim 25, wherein thecontrol unit is adapted to activate each contractile element pulsatoryand alternately independently from each other.
 32. The medical deviceaccording to claim 31, wherein the control unit is designed so that atleast two contractile elements are able to be maintained in theiractivated position at the same time.
 33. The medical device according toclaim 31, wherein the control unit is designed so that at least twocontractile elements are able to be maintained in their resting positionat the same time.
 34. The medical device according to claim 1, whereinthe actuator is designed so that the contractile element applies apressure on an organ to be contracted during a period comprised between30 seconds and 90 minutes.
 35. The medical device according to claim 1,wherein said safety means are designed to move automatically thecontractile element from its activated position into its restingposition if the pressure applied on the organ is higher than a presetpressure.
 36. The medical device according to claim 1, wherein saidsafety means are designed to move automatically the contractile elementfrom its resting position into its activated position if the time forwhich the organ is not constricted is higher than a preset time.
 37. Themedical device according to claim 1, wherein the source of energy isplaced in a power supply unit separated from the control unit andconnected with electric cables, and wherein means for reducing corrosionof the medical device comprise means for providing a current conversionDC/AC/DC between the power supply unit and the control unit.
 38. Methodfor assisting or replacing a natural sphincter, assisting or replacing anatural sphincter using a medical device comprising: an artificialcontractile structure comprising at least one contractile elementadapted to contract an organ, in such way that said contractile elementis in a resting or in an activated position, the activated positionbeing defined with said contractile element constricting the organ andthe resting position being defined with said contractile element notconstricting the organ, at least one actuator, at least one control unitcomprising and controlling said actuator, at least one source of energyfor powering said actuator, wherein said actuator is designed, and inuse operated, to activate said contractile structure in such a way thatthe ratio “current which is needed to maintain the contractile elementin its activated position and in its resting position/current which isneeded to move the contractile element between its activated positionand its resting position” is less than 1/500, means for reducingcorrosion of the medical device, safety means designed to changeautomatically the position of the contractile element, wherein saidsafety means are designed to move automatically the contractile elementfrom its activated position into its resting position if the power ofthe source of energy is less than a preset power, and wherein the atleast one source of energy is an implantable battery in a power supplyunit removably connected to the at least one control unit.
 39. A methodfor assisting or replacing a paralyzed muscle, comprising the use of amedical device comprising: an artificial contractile structurecomprising at least one contractile element adapted to contract anorgan, in such way that said contractile element is in a resting or inan activated position, the activated position being defined with saidcontractile element constricting the organ and the resting positionbeing defined with said contractile element not constricting the organ,at least one actuator, at least one control unit comprising andcontrolling said actuator, at least one source of energy for poweringsaid actuator, wherein said actuator is designed to activate saidcontractile structure in such a way that the ratio “current which isneeded to maintain the contractile element in its activated position andin its resting position/current which is needed to move the contractileelement between its activated position and its resting position” is lessthan 1/500, means for reducing corrosion of the medical device, safetymeans designed to change automatically the position of the contractileelement, wherein said safety means are designed to move automaticallythe contractile element from its activated position into its restingposition if the power of the source of energy is less than a presetpower, and wherein the at least one source of energy is an implantablebattery in a power supply unit removably connected to the at least onecontrol unit.